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Xuezhi Ma1 Yangzhi Zhu2 Qiushi Liu1 Sanggon Kim2 Leonard Apontti2 Da Xu1 Ruoxue Yan2 3 Ming Liu1 3

1, University of California, Riverside, Riverside, California, United States
2, University of California, Riverside, Riverside, California, United States
3, University of California, Riverside, Riverside, California, United States

The silver nanowire (AgNW) represents a novel class of probes for scanning probe microscopes (SPM), including atomic force microscopy (AFM), near-field scanning optical microscopy (NSOM) and tip-enhanced Raman spectroscopy (TERS), due to their unique mechanical and optical characteristics. Here we report our recent advances on the integration of commercial AFM cantilevers with a single sharp-tip AgNWs (5 nm tip radius) through a reliable, cost-efficient bench-top process for high-fidelity and high-resolution (HR) topographic imaging of nanoscale 3D surfaces and nano-antenna-assisted remote-excitation TERS. We have demonstrated that the novel high-aspect-ratio AFM probe is mechanically robust against buckling and bending up to 150 nN, and is capable of high fidelity imaging of deep trenches (10:1) imaging with a lateral resolution of <8 nm, on par with or exceeding the performance of commercial HAR probes fabricated by expensive clean-room techniques. Recently, we have further demonstrated a remote-excitation TERS probe by attaching a silver nanoparticle (AgNP) on AgNW. The AgNP served as a nano-antenna, which remotely couples excitation laser into SPP modes propagating along the AgNW to its tip apex. The remote excitation shrinks the laser illumination area on the sample by up to 10,000 times, thus effectively suppresses the TERS background and avoids sample photo degradation. We have achieved high signal-noise ratio TERS of 4-Aminothiolphenol self-assembled monolayer (SAM) and a sub-50nm spatial resolution chemical mapping of monolayer molybdenum disulfide MoS2.

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